This invention relates to a process for producing 1,3-bis(3-aminophenoxy)benzene.
1,3-Bis(3-aminophenoxy)benzene (hereinafter abbreviated to APB) is an important material which is used as a monomer for heat-resistant high molecular weight polymers, particularly as a raw material for polyamides and polyimides.
For example, an acetylene-terminated polyimide produced from APB, 3,3',4,4'-benzophenonetetracarboxylic acid dianhydride and 3-aminophenylacetylene has been known to be a polymer ranked as one of those having a highest heat resistance among polyimides (U.S. Pat. No. 3,845,018; U.S. Pat. No. 3,879,349).
As to processes for producing APB, a process of condensing resorcin with 1-bromo-3-nitrobenzene followed by reduction (German patent application laid-open No. 2,462,112) and a process of condensing 3-aminophenol with 1,3-dibromobenzene (W. Fin et al, Helv. Chim. Acta, 51, 971 (1968); U.S. Pat. No. 4,222,962) have been known.
In the case of the above reaction of resorcin with 1-bromo-3-nitrobenzene among the above processes for producing APB, resorcin is first treated with sodium methoxide in a large amount of benzene, followed by carrying out dehydration operation while recovering benzene by distillation to form resorcindisodium which is then reacted with 3-nitrobromobenzene in the presence of cuprous chloride in a large amount of pyridine solvent under argon stream to obtain 1,3-bis(3-nitrophenoxy)benzene (yield; 41%) which is then reduced with ferrous sulphate to obtain the objective compound.
Further according to the production process of condensing 3-aminophenol with 1,3-dibromobenzene, the both are reacted at 200.degree..about.280.degree. C. in the presence of copper powder or reacted in the presence of cuprous chloride in a large amount of pyridine to produce the objective compound, but the yield is as low as 45.about.65%.
As described above, as to known processes for producing APB, .circle.1 a reaction solvent such as pyridine having a drawback of handling with respect of disagreeable smell is used in a large amount; further .circle.2 a dehydration solvent such as benzene is used in a large amount in order to inhibit side reactions such as hydrolysis; thus an operation of strict moisture removal is required; moreover .circle.3 since a reaction promotor such as copper powder, cuprous chloride or the like is used, caution should be paid as to coloring, removal of copper ion, etc.; still further .circle.4 reaction is carried out in an inert gas; hence it is very difficult to commercially practice these processes in view of production operations, converting disposed materials into non-public-pollution materials, etc.